Cross flow filtration apparatuses are described in the patent literature, for example, in the Swedish Publication Prints SE 451429, 457607, 459475, 463241 and 465040. Methods based on the use of such apparatuses are successfully applied for separating solid constituents from a liquid phase and for separation of liquid from liquid, for example, for separation of oil from water. The above mentioned Publication Print SE 463241 describes such a fluid/fluid separation method.
SE 459475 describes a separation device comprising several adjacently arranged cells. FIG. 1 shows a section of such a stack. Each unit or cell consists of a plate 10 provided with a central opening through which extends a shaft 11 provided with rotor blades 12. On each side of the plate 10 a filter 15 is fastened by means of clamp rings 13 and 14. The liquid to be treated is supplied through a common channel 16 formed by through-holes in the plates 10. The liquid stream is supplied into the chamber 17, whereby part of it (the permeate) passes through the filter and is gathered via channels 18 in the plate to be finally discharged through a common outlet (not shown). The portion of the liquid flow (the reject) which does not penetrate through the filter, is discharged through holes in the plate. Said holes form a common conduit 19 for the outgoing reject. The liquid is pushed across the filter surface 15 by means of the rotor blades 12.
When the filter is changed in the above mentioned device the plate containing the filter to be changed is taken out. The removing of the plate itself from the stack is carried out relatively easy in a way more closely described in the Publication Print in question. However, the removal of the used filter from the plate and inserting of a new filter is very time consuming and hard because the filter is fastened by means of numerous screws to the clamp rings securing the filter to the plate. This causes for its part long shutdowns in the separation plant.